Question: Simplify the following expression: $x = \dfrac{4n}{9} - \dfrac{n}{10}$
Explanation: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $9$ and $10$ $\lcm(9, 10) = 90$ $ x = \dfrac{10}{10} \cdot \dfrac{4n}{9} - \dfrac{9}{9} \cdot \dfrac{n}{10} $ $x = \dfrac{40n}{90} - \dfrac{9n}{90}$ $x = \dfrac{40n -9n}{90}$ $x = \dfrac{31n}{90}$